Greybeard was right: this is a pressure vessel. It's a welded aluminum sphere [circumferentially welded] with a carbon-fiber overlay and a polyurethane top coat. Hopefully you can read the labeling on the bottle to see more about it. I have one of these that's burst, too ... it's pretty scary. It's in my boss's office, though, so I'll have to sneak in and take a shot.